Method for adjusting adaptive programme maps of an adaptive knock control in an internal combustion engine and a method for adjusting the knock control in said engine

ABSTRACT

Proposed is a method for adjusting an adaptive characteristics map of an adaptive engine-knock control system and a method for adaptively controlling engine knock, the adaptive characteristics map ( 20 ) being defined by at least one operating parameter ( 22, 24 ), the adaptive characteristics map ( 20 ) for each operating-parameter range ( 26 ) being made up of a precontrol component (bi) that characterizes the ambient conditions, and a residual component (ai) that results from the engine-knock control, the value of the adaptive characteristics map for each operating-parameter range being given by the sum of the precontrol component (bi) corresponding to the specific operating-parameter range, and the residual component (ai) corresponding to the specific operating-parameter range. In this context, the adjustment of the adaptive characteristics map is carried out by initially determining if ambient conditions have changed, and by subsequently ascertaining a new precontrol component as a function of the changed ambient conditions for each operating-parameter range, if the ambient conditions have changed, or by holding the precontrol component constant for each operating-parameter range, if the ambient conditions have not changed.

BACKGROUND INFORMATION

[0001] The present invention starts out from a method for adjusting anadaptive characteristics map of an adaptive engine-knock control systemand a method for adaptively controlling the knock of an internalcombustion engine, according to the species defined in the independentclaims.

[0002] A method for adjusting an adaptive characteristics map of anadaptive engine-knock control system is already known, where, in eachcase, current ignition-retard values are written to an adaptivecharacteristics map continuously, or in specific time intervals. In theevent of a sharp change in the ambient conditions, for example whenusing a fuel that is less knock-resistant, the adaptivecharacteristics-map value is slowly adjusted as a function of theoccurring knock signals, and each characteristics-map range must beentered at least once, in order to adjust the entire adaptivecharacteristics map.

[0003] A method for adaptively controlling the knock of an internalcombustion engine is known from DE 40 08 170 A1, where the currentignition-retard values are stored in an adaptive characteristics map.The adaptive characteristics map has subdivided ranges dependent on atleast one operating parameter of the internal combustion engine, onevalue of ignition retard always being stored in the appropriate range,during operation. Upon shifting to another operating-parameter range,the ignition-retard value stored for this operating-parameter rangeforms the new ignition-retard value, which is the starting point for theengine-knock control. The characteristics-map value is adapted in thespecific operating-parameter range in accordance with the signal of theengine-knock control system, the ignition being retarded in response toengine knock. If no engine knock occurs over a certain period of time,the ignition timing is advanced again.

SUMMARY OF THE INVENTION

[0004] In comparison with the known methods, the method of the presentinvention for adjusting an adaptive characteristics map of an adaptiveengine-knock control system has the advantage that, in response to asharp change in the ambient conditions, the ignition-retard value isimmediately adapted without unnecessary engine knock occurring. Itshould be regarded as a further advantage, that the entire adaptivecharacteristics map is adjusted to the modified ambient conditions,which likewise results in prevention of unnecessary engine knock, andthe new ambient conditions are already taken into consideration inresponse to changing to a new operating-parameter range. The measuresset forth in the dependent claims render possible an advantageousfurther refinement and improvement of the method for adjusting anadaptive characteristics map specified in the independent claim. It isparticularly advantageous that a change in the ambient conditions isdetected, when the currently required ignition-retard value markedlydiffers from a reference angle corresponding to the specificoperating-parameter range. Therefore, such a change in the ambientconditions may be detected easily and quickly. In this context, it isadvantageous to generate a reference value from the current adaptivecharacteristics-map values. Upon detecting a change in the ambientconditions, it is also advantageous to calculate a factor, whichdescribes which range between the worst possible adaptivecharacteristics-map value and the best possible adaptivecharacteristics-map value contains the current ignition-retard value, sothat adaptive characteristics-map values may then be adjusted for eachoperating-parameter range in accordance with the factor. Thus, it ispossible to adjust the entire adaptive characteristics map in a simpleand quick manner. It is particularly simple to calculate the factor,when a straight line is interpolated between the best possiblecharacteristics-map value and the worst possible characteristics-mapvalue. It is likewise advantageous to establish the change in ambientconditions, using sensor values, since this allows the ambientconditions to be assessed in a more objective manner. The ambienttemperature or the fuel quality especially influence the knockfrequency. Therefore, is advantageous to monitor these conditions, usingsensors. In the case of monitoring the ambient conditions, usingsensors, it is also advantageous to characterize the new ambientconditions with respect to the best possible and worse possible ambientconditions, using a factor, as well as to ascertain the adaptivecharacteristics map adjusted to the new ambient conditions, using thefactor. Consequently, it is once again possible to adjust the entireadaptive characteristics map in a simple manner. Furthermore, it isadvantageous to design the adaptive characteristics map in acylinder-selective manner and therefore adjust the adaptivecharacteristics map in a cylinder-selective manner, as well.

[0005] In comparison with the known method, the method of the presentinvention for adaptively controlling the knock of an internal combustionengine, having the features of the independent claim, has the advantagethat the ambient conditions are taken into consideration, it beingpossible to react very quickly to changed ambient conditions. Inaddition, it is advantageous that operating-state changes characterizedby the occurrence of engine knock may be detected very quickly. it Sinceeach cylinder or each cylinder group has its own combustioncharacteristics, it is, in this case, advantageous to implement theadaptive engine-knock control in a cylinder-selective orcylinder-group-selective manner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Exemplary embodiments of the present invention are shown in thedrawings and are explained in detail in the following description. Thefigures show:

[0007]FIG. 1 a schematic of a method of the present invention foradjusting an adaptive characteristics map of an adaptive engine-knockcontrol system;

[0008]FIG. 2 a schematic of an adaptive characteristics map;

[0009]FIG. 3 a schematic of a first and a second limitingcharacteristics map; and

[0010]FIG. 4 a schematic of the calculation of a reference factor.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0011] During the operation of an internal combustion engine, so-calledengine knock represents a critical operating state that can unfavorablyaffect the service life. A so-called engine-knock control system isknown, which retards the ignition in response to detecting knock in acylinder of the engine. This allows the knocking condition to beeliminated. If no engine knock occurs after a certain period of timeelapses, then the ignition timing is advanced again. In order to obtain,in a particularly rapid manner, an ignition-retard value at which noknock occurs, in response to changing operating-parameter ranges, aso-called adaptive characteristics map is made available in the memoryof a control unit. This is described in detail in DE 40 08 170. Thisadaptive characteristics map, which is defined by at least one operatingparameter, is subdivided into specific, fixed ranges. For each range,the memory receives an ignition-retard value that saves the specificignition-retard value set upon leaving the operating-parameter range. Inthe event of a repeated shift into the specific operating-parameterrange, the ignition-retard value stored there is set and used as astarting point for controlling engine knock. Therefore, in the event ofa change of operating-parameter ranges, the ignition-retard valuesoptimal for controlling engine knock may be set very rapidly. In thiscontext, operating parameters include, in particular, the load and theengine speed.

[0012] Ignition-retard values are not only a function of operatingparameters, but also a function of ambient conditions, in particular thequality of the fuel, i.e. the knock resistance of the fuel, and theambient temperature. In response to a change in the ambient conditions,e.g. when using another fuel, the ignition-retard value is significantlyaffected to some extent. In order to take this dependence into account,the present invention now provides for each ignition-retard valuecontained in an adaptive characteristics map being expressed as a sum ofa precontrol component bi and a residual component ai. In this context,the precontrol component contains the portion of the ignition-retardvalue that is a function of the ambient conditions, and residualcomponent ai contains the portion of the ignition-retard value that isdirectly affected by the engine-knock control. Such an adaptivecharacteristics map is shown schematically in FIG. 2. The adaptivecharacteristics map represented in FIG. 2 is exemplarily depicted fortwo operating parameters, e.g. the load or the engine speed. However,such a characteristics map may also be defined by one operatingparameter or more than two operating parameters. Values of a firstoperating parameter, e.g. the load, are plotted on axis 22. Values of asecond operating parameter, e.g. the engine speed, are plotted on axis24. If the values of the axis of first operating parameter 22 and secondoperating parameter 24 are now subdivided into individual ranges, then amatrix of operating-parameter ranges 26 is formed, as is represented inFIG. 2. All of the operating-parameter ranges 26 together defineadaptive characteristics map 20. Each such operating-parameter range isnow assigned a residual component ai and a precontrol component bi, asis exemplarily represented in operating-parameter range 27. Therefore,adaptive characteristics map 20 has a number of precontrol-componentvalues bi corresponding to the number of operating-parameter ranges, aswell as the same number of residual-component values ai. Therefore, theadaptive characteristics map contains a total of twice as many values asthe operating-parameter ranges. In this context, the ignition-retardvalue is expressed by the sum of residual component ai and precontrolcomponent bi for each operating-parameter range.

[0013] The method of the present invention for adjusting the adaptivecharacteristics map of an adaptive engine-knock control system isschematically represented in FIG. 1. In this context, it is determinedin step 3 if the ambient conditions have changed. If this is the case,then the method resumes with step 6. In step 6, a criterion isdetermined, with the aid of which a new precontrol component bi isdetermined in the subsequent step 10, for each operating-parameter range26 of adaptive characteristics map 20. The method then repeats step 3.If the determination in step 3 has established that the ambientconditions have not changed, then, in step 15, the precontrol-componentvalue bi of each operating-parameter range 26 of adaptivecharacteristics map 20 is retained in unmodified form. In this case, themethod also repeats step 3 after step 15. The continuation of the methodwith step 3 is generally carried out in specific time intervals. Themethod represented with the aid of FIG. 1 ensures that, for eachoperating-parameter range 26, adaptive characteristics map 20 is veryquickly adjusted to the changed ambient conditions. This is advantageoussince, in this manner, unnecessary incidences of engine knock areprevented, and the destruction of the internal combustion engine isprevented.

[0014] In a preferred exemplary embodiment, the determination of whetheror not the ambient conditions have changed is carried out, using thecurrent ignition-retard value determined by the engine-knock controlsystem. In this context, the current ignition-retard value determined bythe engine-knock control system is compared to a reference valueassigned to the current operating parameters, and it is determined if afirst threshold value is exceeded. When a first threshold value isexceeded, i.e. the current ignition-retard value sharply deviates fromthe reference value, it is concluded that the ambient conditions havemarkedly changed, that is to say, the method is continued with step 6.If the first threshold value is not exceeded, it is then concluded thatthe ambient conditions have not changed or have only changed to a verysmall extent, that is to say, the method is continued with step 15. In apreferred exemplary embodiment, such a reference value is represented bythe specific adaptive characteristics-map value, which is present forthe corresponding operating-parameter range and results from the sum ofresidual component ai and precontrol component bi. In another preferredexemplary embodiment, such a reference value is ascertained in a masterrange, in that, for example, several adjacent operating-parameter rangestogether form a master range, and an average value of the adaptivecharacteristics-map values is calculated as a reference value from theseoperating-parameter ranges belonging to the master range. In thiscontext, the adaptive characteristics-map value of eachoperating-parameter range is in turn calculated from specific residualcomponent ai and specific precontrol component bi. In this context, suchan average value can be, for example, the arithmetic mean of theadaptive characteristics-map values.

[0015] In a preferred exemplary embodiment of the present invention, twofurther characteristics maps are present in a memory of a control unit,the two characteristics maps being defined by at least one operatingparameter, and containing limiting characteristics-map values of theincidences of ignition retard, for the worst possible combination ofambient conditions and the best possible combination of ambientconditions. Two such characteristics maps are represented in FIG. 3. Ineach case, a first operating parameter is again plotted on axis 22, anda second operating parameter is again plotted on axis 24. If, asmentioned above, adaptive characteristics map 20 is defined by one ormore than two operating parameters, then the limiting characteristicsmaps for the best and worst possible combinations of ambient conditionsare accordingly defined by one or more than two operating parameters, aswell. Once again, the two operating parameters are subdivided intoindividual ranges to form a matrix of ranges, each so-called masterrange being assigned a limiting characteristics-map value. Representedin FIG. 3a is a first limiting characteristics map 30 having masterranges 36, each master range 36 being assigned a limitingcharacteristics-map value bui. The first limiting characteristics mapcontains the limiting characteristics-map values of the ignition retardfor the worst possible ambient conditions. Represented in FIG. 3b is asecond limiting characteristics map 40 having master ranges 46, eachmaster range being assigned a limiting characteristics-map value boi.The second limiting characteristics map 40 contains the limitingcharacteristics-map values of the ignition retard for the best possibleambient conditions. Master ranges 36 and 46 of the first and secondlimiting characteristics maps, respectively, correspond tooperating-parameter ranges 26 of adaptive characteristics map 20. In afurther exemplary embodiment, master ranges 36 and 46 of the first andsecond limiting characteristics maps, respectively, are also formed fromseveral operating-parameter ranges 26.

[0016] In order to now ascertain the precontrol component for eachoperating-parameter range 26 in accordance with the changed ambientconditions, a first factor z, which describes where currentignition-retard value xj 55 lies between first limitingcharacteristics-map value ruj and second limiting characteristics-mapvalue roj, is calculated as represented in FIG. 5. In this context,limiting characteristics-map values ruj and roj are extracted frommaster ranges 38 and 48, respectively, of the first and second limitingcharacteristics maps, the master range containing the values of theoperating parameters, which correspond to the current values of theoperating parameters of the current ignition-retard value. Limitingcharacteristics-map values ruj and roj of first limiting characteristicsmap 30 and second limiting characteristics map 40, respectively, arepreferably joined by a straight line, and first factor z is calculatedaccording to the following formula:$z = \frac{{xj} - {ruj}}{{roj} - {ruj}}$

[0017] In other exemplary embodiments, limiting characteristics-mapvalues ruj and roj of first limiting characteristics map 30 and secondlimiting characteristics map 40, respectively, are joined by othercurves, the calculation of first factor z then being carried out inaccordance with the curve used.

[0018] In the preferred exemplary embodiment, the precontrol componentis now ascertained for each operating-parameter range 26 in such amanner, that, for each operating-parameter range 26, the corresponding,first limiting characteristics-map value and the distance between thefirst and second limiting characteristics-map values (roi−rui)multiplied by factor z are added, and a first intermediate value isascertained for each operating-parameter range 26. A further exemplaryembodiment provides that, for each operating-parameter range 26, thedistance between the first and second limiting characteristics-mapvalues (roi−rui) multiplied by factor z is subtracted from thecorresponding, second limiting characteristics-map value, and in thismanner, a second intermediate value is ascertained for eachoperating-parameter range 26. Then, in a preferred exemplary embodiment,the residual component ai stored for the specific operating-parameterrange is subtracted from the first and second intermediate value foreach operating-parameter range 26.

[0019] In a further, preferred embodiment, sensors are used to determineif the ambient conditions have changed. In this context, the ambienttemperature is measured by, e.g. a temperature sensor and transmitted tothe control unit. Alternatively, or in addition, the fuel quality, e.g.the knock resistance, is determined by a further sensor and likewisetransmitted to the control unit. If the change in the ambient conditionsexceeds a second threshold value, this being determined in step 3, thenthe method is continued with step 6. The ambient conditions ascertainedare compared to the best and worst possible ambient conditions, and asecond factor f is calculated, which describes where the ambientconditions present at the specific time are located between the best andworst possible ambient conditions. The method may subsequently becontinued as described above, and a new precontrol component bi may becalculated for each operating-parameter range 26. In this context,second factor f is used instead of first factor z.

[0020] In a further preferred embodiment, for example in acylinder-specific engine-knock control system, an adaptivecharacteristics map is prepared in the memory of the control unit, foreach cylinder or for each fixed cylinder group. Each adaptivecharacteristics map has, in each case, the number ofprecontrol-component values ai and residual-component values bicorresponding to the number of operating-parameter ranges. This may alsobe achieved by providing an adaptive characteristics map in the memoryof the control unit, the adaptive characteristics map containing aprecontrol-component value ai and a residual-component value bi for eachoperating-parameter range, for each cylinder or each cylinder group.During the determination of whether or not the ambient conditions havechanged, the average value of all the current ignition-retard values ofthe cylinders or cylinder groups is compared to a reference valueassigned to the current operating parameters. Such a reference valuecould be the adaptive characteristics-map value for the specificcylinder or specific cylinder group, in the current operating-parameterrange or master range. If the above-described threshold-value comparisonreveals that the ambient conditions have changed, then the precontrolcomponent for each cylinder or each cylinder group is adapted to the newambient conditions in accordance with the above-described method.

[0021] After the ambient conditions are changed, the adaptivecharacteristics-map value read from adaptive characteristics map 20 istherefore given by the sum of residual component ai and the precontrolcomponent bi that has now been determined anew. Precontrol component biwas adjusted for each operating-parameter range, so that an adaptivecharacteristics-map value adjusted to the new ambient conditions is alsopresent in the event of a shift into a new operating-parameter range 26.

What is claimed is:
 1. A method for adjusting an adaptationcharacteristics map of an adaptive engine-knock control system, theadaptive characteristics map (20) being defined by at least oneoperating parameter (22, 24), the adaptive characteristics map (20) foreach operating-parameter range (26) being made up of a precontrolcomponent (bi) that characterizes the ambient conditions and a residualcomponent (ai) that results from the engine-knock control, the value ofthe adaptive characteristics map for each operating-parameter rangebeing given by the sum of the precontrol component (bi) corresponding tothe specific operating-parameter range, and the residual component (ai)corresponding to the specific operating-parameter range, using thefollowing steps: a) determining if a change in the ambient conditionshas occurred; and b) ascertaining a new precontrol component (bi) foreach operating-parameter range, as a function of the changed ambientconditions, if the ambient conditions have changed; or holding theprecontrol component (bi) constant for each operating-parameter range,if the ambient conditions have not changed.
 2. The method as recited inclaim 1, wherein a precontrol component (bi) and a residual component(ai) are provided for each cylinder or each cylinder group, and, inresponse to determining that a change in the ambient conditions hastaken place, the precontrol component (bi) is recalculated for eachcylinder or each cylinder group, for each operating-parameter range. 3.The method as recited in claim 1, wherein a change in the ambientconditions is detected, when the difference between an ignition-retardvalue currently required and a reference value taken from the adaptivecharacteristics map exceeds a specific, fixed, first threshold value. 4.The method as recited in claim 3, wherein the reference value taken fromthe adaptive characteristics map is calculated as an average value froma master range of the adaptive characteristics map corresponding to thecurrent operating parameters.
 5. The method as recited in claim 3,wherein the reference value taken from the adaptive characteristics mapcorresponds to the adaptive characteristics-map value for the currentoperating parameters.
 6. The method as recited in claim 3, whereinbetween a first limiting characteristics-map value (ruj), the firstlimiting characteristics map representing a characteristics map of theignition-retard values for the worst possible ambient conditions; and asecond limiting characteristics-map value (roj) contained in the memoryunit, the second limiting characteristics map representing acharacteristics map of the ignition-retard values for the best possibleambient conditions, in which the master range corresponding to thecurrent operating parameters is interpolated; a first reference factor(z) is determined in accordance with the position of the current,required ignition-retard value (xj) between the first limitingcharacteristics-map value (ruj) corresponding to the current operatingparameters and the second limiting characteristics-map value (roj)corresponding to the current operating parameters, on an interpolationcurve (51) connecting the first and second limiting characteristics-mapvalues.
 7. The method as recited in claim 6, wherein the interpolationcurve (51) between the first and the second limiting characteristics-mapvalues (ruj, roj) is a straight line for the specificoperating-parameter range.
 8. The method as recited in claim 1, whereina change in the ambient conditions is detected, when at least one changein the value measured by at least one sensor exceeds a second, fixedthreshold value, the at least one sensor measuring ambient conditions.9. The method as recited in claim 8, wherein the ambient temperature orthe fuel quality represents the ambient conditions measured by the atleast one sensor.
 10. The method as recited in claim 8, wherein thecurrent ambient conditions are compared to the best possible and theworst possible ambient conditions, and a second reference factor (f) isascertained as a function of the deviation of the current ambientconditions from the worst possible or best possible ambient conditions.11. The method as recited in one of claims 6 or 10, wherein the newprecontrol component for each operating-parameter range is ascertainedin such a manner, that, for each operating-parameter range, thedifference (roj−ruj) multiplied by the calculated, first or secondreference factor (z or f) is added to or subtracted from the first andsecond limiting characteristics-map values (ruj and roj), the specificvalue of the residual component being subsequently subtracted for eachoperating-parameter range.
 12. A method for adaptively controlling theknock of an internal combustion engine, an ignition-retard value beingread from an adaptive characteristics map (20) and ignition-retardvalues being written into an adaptive characteristics map (20), theadaptive characteristics map being defined by at least one operatingparameter (22, 24), the adaptive characteristics map (20) for eachoperating-parameter range (26) being made up of a precontrol component(bi) that characterizes the ambient conditions and a residual component(ai) that results from the engine-knock control, the value of theadaptive characteristics map (20) for each operating-parameter range(26) being given by the sum of the precontrol component (bi)corresponding to the specific operating-parameter range and the residualcomponent (ai) corresponding to the specific operating-parameter range.13. The method as recited in claim 12, wherein, in the adaptivecharacteristics map (20), a precontrol component (bi) and a residualcomponent (ai) are provided in each operating-parameter range, for eachcylinder or each cylinder group.